In three-dimensional integrated circuits, a device die may be stacked on another device die, or stacked on an interposer, a package substrate, and the like. Through-substrate vias (TSVs) are used to make electrical connections from one side of, for example, an interposer to the opposite side. An interposer may include many TSVs therein.
Increasingly more interposers are formed in semiconductor substrates such as silicon substrates. During the use of the interposers, the respective semiconductor substrates may be electrically grounded or may be electrically floating. Each of the TSVs is separated from the respective semiconductor substrate by an insulation layer. Accordingly, a TSV forms a capacitor with the insulation layer and the substrate, with the TSV and the substrate acting as two capacitor plates, and the insulator acting as the capacitor insulating layer. When the substrate is electrically floating or has an imperfect grounding, signals in TSVs are coupled to the semiconductor substrate, and are further coupled to other TSVs. Each of the TSVs thus acts as a noise source for other TSVs.
Some of the signals that are transferred through the TSVs might be more prone to the effect of the noise from other TSVs. For example, analog signals and weak digital signals are more likely to be affected. Such adverse effect needs to be reduced.